Pump device

ABSTRACT

A pump device includes: a variable capacity-type pump unit configured to include an inner rotor having a plurality of external teeth , an outer rotor having a plurality of internal teeth meshing with a portion of the plurality of external teeth of the inner rotor, a housing, a suction port and a discharge port, an adjustment member adjusting a discharge pressure of a fluid, a biasing mechanism biasing the adjustment member, a control flow passage causing a fluid pressure from the discharge port to be applied to the adjustment member, a solenoid valve adjusting the fluid pressure applied to the adjustment member, a bypass flow passage, and a relief valve; a rotation speed sensor measuring a rotation speed of a drive source; and a control unit controlling the solenoid valve.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119to Japanese Patent Application 2018-039948, filed on Mar. 6, 2018, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a pump device.

BACKGROUND DISCUSSION

JP 2011-256987A (Reference 1) discloses the following technique. Inorder to perform a speed change control process of an automatictransmission, there is provided a linear solenoid valve which controls ahydraulic pressure for supplying hydraulic operating oil to a frictionelement. When the hydraulic operating oil serving as the hydraulicpressure having an output hydraulic pressure target value is suppliedfrom the linear solenoid valve, a command current is calculated, basedon a map of the command current vs a command hydraulic pressure which isprepared for each individual linear solenoid valve.

According to Reference 1, a difference between an actual outputhydraulic pressure and the command hydraulic pressure is calculated bysweeping the command current, and a reference map previously preparedbased on the difference is corrected so as to prepare the map of thecommand current vs the command hydraulic pressure. In order to performthe automatic transmission based on the prepared map of the commandcurrent vs the command hydraulic pressure, an individual difference ofelectrohydrostatic control means is reduced so as to realize improvedcontrol accuracy.

JP 2005-155920A (Reference 2) discloses the following technique. Aparametric variable relating to hydraulic pressure characteristics of asolenoid valve used for the automatic transmission is stored in amemory, and the parametric variable stored in the memory is called up.Based on the parametric variable, a target current for a targethydraulic pressure is calculated.

According to Reference 2, as an automatic transmission system, optimumvirtual map identification information and the parametric variable whichare stored in the memory are called up so as to select an optimumvirtual map. Based on selection of the optimum virtual map and theparametric variable, the target current to be supplied to a targetsolenoid valve is calculated.

JP 2016-98768A (Reference 3) discloses the following technique for anoil pump. The oil pump includes a solenoid valve that has an inner rotorhaving external teeth, an outer rotor having internal teeth, and anadjustment ring for regulating a discharge amount of the hydraulicoperating oil by adjusting a position, and that controls a pressureapplied to the adjustment ring from a discharge port. The oil pumpoperates the adjustment ring by controlling the solenoid valve so as tocontrol the discharge amount of the hydraulic operating oil.

According to Reference 3, the oil pump includes a coil spring whichbiases the adjustment ring in a direction in which a discharge pressureof the discharge port increases. The pressure applied to the adjustmentring is raised by controlling the solenoid valve. In this manner, theadjustment ring is operated against a biasing force of the coil spring.An operating form is set so as to reduce the discharge pressure in thedischarge port.

According to the techniques respectively disclosed in References 1 and2, a current value to be supplied to an electromagnetic solenoid iscalculated based on the map so as to realize proper control by using thecurrent value calculated in this way. However, viscosity of thehydraulic operating oil increases at a low temperature. Accordingly, itis necessary to consider a temperature when the current value to besupplied to the electromagnetic solenoid is set. However, the techniquesrespectively disclosed in References 1 and 2 do not take the temperatureinto consideration. Consequently, there is room for improvement.

Here, as disclosed in Reference 3, it is conceivable to use a pump whichcan change the discharge pressure. However, even though the pump isconfigured in this way, the discharge pressure is greatly affected bythe temperature of the hydraulic operating oil. For example, even if themap is set using the techniques respectively disclosed in References 1and 2 and the control is performed by calculating the current value tobe supplied to the solenoid valve based on the map, it is difficult toobtain a target discharge pressure.

In order to eliminate this disadvantage, it is conceivable to set tabledata which takes the temperature into consideration. However, ifcontrolling of a variable capacity-type pump disclosed in Reference 3 isconsidered, the table data has a data structure in which a current to besupplied to the solenoid valve is calculated based on rotation speed(rotation speed per unit time) of a drive source of the pump, capacityof the set pump, and an oil temperature. Accordingly, the table datarequires a huge amount of data, and a nonvolatile memory having largecapacity is required. In addition, if the table data has the huge amountof data, a process becomes complicated when the table data is set.

Thus, a need exists for a pump device which is not susceptible to thedrawback mentioned above.

SUMMARY

A feature of a pump device according to an aspect of this disclosureresides in that the pump device includes a variable capacity-type pumpunit configured to include an inner rotor having a plurality of externalteeth and rotatable around a first shaft core, an outer rotor having aplurality of internal teeth meshing with a portion of the plurality ofexternal teeth of the inner rotor and rotatable around a second shaftcore, a housing accommodating the inner rotor and the outer rotor, asuction port and a discharge port which are formed in the housing, anadjustment member rotatably supporting the outer rotor and adjusting adischarge pressure of a fluid in the discharge port by changing apositional relationship between the first shaft core and the secondshaft core, a biasing mechanism biasing the adjustment member in adirection in which the discharge pressure is increased or decreased, acontrol flow passage causing a fluid pressure from the discharge port tobe applied to the adjustment member to apply a pressure to theadjustment member against a biasing force of the biasing mechanism, asolenoid valve interposed in the control flow passage in order to adjustthe fluid pressure to be applied to the adjustment member, a bypass flowpassage causing the fluid of the discharge port to flow into the suctionport, and a relief valve disposed in the bypass flow passage so as to bebrought into an open state when the discharge pressure reaches apredetermined value or more, a rotation speed sensor measuring arotation speed per unit time of a drive source that drives the innerrotor or the outer rotor, and a control unit controlling the solenoidvalve. The control unit includes a pressure value conversion unit thatconverts a target discharge pressure into a conversion target dischargepressure serving as position information within a predetermined range,in a definition region where a maximum discharge pressure and a minimumdischarge pressure which are set based on the rotation speed of thedrive source and a temperature of the fluid are respectively defined asa maximum value and a minimum value in the predetermined range, a mapdata selection unit that stores first map data in which the relief valveis brought into an open state in the maximum discharge pressure andsecond map data in which the relief valve is brought into a closed statein the maximum discharge pressure, as map data having a data structurerepresented by an orthogonal coordinate system in which the definitionregion is denoted in a direction of a target axis and a target currentvalue of the solenoid valve is denoted in a direction of an output axisorthogonal to the target axis, and that selects any one of the first mapdata and the second map data, based on the rotation speed of the drivesource measured by the rotation speed sensor and the temperature of thefluid measured by a temperature sensor, and an output current controlunit that acquires the target current value corresponding to theconversion target discharge pressure with reference to the selected mapdata, and that outputs the target current value to the solenoid valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of thisdisclosure will become more apparent from the following detaileddescription considered with the reference to the accompanying drawings,wherein:

FIG. 1 is a hydraulic pressure circuit diagram illustrating aconfiguration of a pump control device;

FIG. 2 is a sectional view of a pump unit for which a discharge pressureis set to a maximum;

FIG. 3 is a sectional view of the pump unit for which the dischargepressure is set to a minimum;

FIG. 4 is a block circuit diagram of a control unit;

FIG. 5 is a view illustrating a relationship between a target hydraulicpressure and a conversion target hydraulic pressure;

FIG. 6 is a view illustrating a shape of map data;

FIG. 7 is a view illustrating representative map data;

FIG. 8 is a graph illustrating a relationship between a hydraulicpressure and a current at mutually different rotation speeds when atemperature of a fluid is 0° C.;

FIG. 9 is a graph illustrating a relationship between the hydraulicpressure and the current at mutually different rotation speeds when thetemperature of the fluid is 30° C.;

FIG. 10 is a graph illustrating a relationship between the hydraulicpressure and the current at mutually different rotation speeds when thetemperature of the fluid is 60° C.;

FIG. 11 is a graph illustrating a relationship between the hydraulicpressure and the current at mutually different rotation speeds when thetemperature of the fluid is 90° C.;

FIG. 12 is a view illustrating a map data correspondence table; and

FIG. 13 is a flowchart of a discharge pressure control routine.

DETAILED DESCRIPTION

Hereinafter, embodiments disclosed here will be described with referenceto the drawings.

Basic Configuration

As illustrated in FIG. 1, a pump device 100 is configured to include avariable capacity-type pump unit P driven by an engine E as a drivesource, a solenoid valve V for controlling a hydraulic pressure(hereinafter, also referred to as a discharge pressure) of oil (exampleof a fluid) discharged from the pump unit P, and a control unit C forcontrolling the solenoid valve V, based on a measuring result of arotation speed sensor SR and a measuring result of a temperature sensorST.

The pump device 100 is installed in a vehicle such as a passenger car.The pump unit P is driven by the engine E of the vehicle, and suctionsthe oil of an oil pan of the engine E by using a suction flow passage 1so as to supply the oil via a supply flow passage 2. The vehicleincludes a hydraulic pressure actuator 3 such as a valve timingcontroller for setting opening and closing timings of an intake valve ofthe engine E and a hydraulic pressure-type transmission, and a maingallery 4 for lubricating the engine E. The oil is supplied thereto fromthe supply flow passage 2. The pump device 100 may be configured tosupply water or chemicals in addition to the oil.

As illustrated in FIG. 1, the pump device 100 includes a supply flowpassage 2, a control flow passage 5, and a drain flow passage 6. Thesolenoid valve V is interposed in the control flow passage 5, and thecontrol flow passage 5 supplies a portion of the oil (example of thefluid) to be fed to the supply flow passage 2 to a pressure chamber PS(refer to FIG. 2) of the pump unit P via the solenoid valve V. The drainflow passage 6 discharges the oil of the pressure chamber PS via thesolenoid valve V.

The control unit C functions as an ECU for controlling an oil pressure.A measuring signal of the rotation speed sensor SR which acquires arotation speed per unit time (hereinafter, abbreviated as a “rotationspeed”) of a crankshaft of the engine E (example of a drive source,hereinafter, abbreviated as the “engine E”) and a measuring signal fromthe temperature sensor ST which measures an oil temperature (temperatureof the fluid) of the oil suctioned by the pump unit P are input to thecontrol unit C.

In a case where the control unit C acquires a target hydraulic pressure(example of a target discharge pressure) from the outside, the controlunit C acquires a target current value with reference to map data M(FIG. 5), and drives the solenoid valve V (strictly, an electromagneticsolenoid of the solenoid valve V) by using the target current value. Inthis manner, a control form is adopted so as to supply the oil having aproper target discharge pressure (this control form will be describedlater).

FIG. 1 illustrates a two position switching type in which spools are setat 2 positions as the solenoid valve V. The solenoid valve V is notlimited to this configuration. For example, a relief valve or an unloadvalve may be used which can adjust the fluid pressure applied to thepressure chamber PS (refer to FIG. 2) via the control flow passage 5 byelectromagnetically controlling a relief pressure. The solenoid valve Vis held at an initial position illustrated in FIG. 1 in a case where adrive current is not supplied to the solenoid valve V (the solenoidvalve V is not driven). In this manner, the control flow passage 5 andthe drain flow passage 6 communicate with each other, and the pressureof the pressure chamber PS is reduced to an atmospheric pressure. Inaddition, in a case where the drive current is supplied to the solenoidvalve V (in a case where the solenoid valve V is driven), as the drivecurrent increases, a flow of the oil is blocked in the drain flowpassage 6, and concurrently, the hydraulic pressure acting on thepressure chamber PS from the control flow passage 5 increases.

Pump Unit

As illustrated in FIGS. 2 and 3, in the pump unit P, a housing H havinga suction port 11 and a discharge port 12 accommodates an inner rotor14, an outer rotor 15, and an adjustment mechanism 20.

The inner rotor 14 has a plurality of external teeth 14A, is rotatablysupported around a driving shaft core X (example of a first shaft core),and is rotated in a direction indicated by an arrow in the drawing by adrive shaft 13 driven using the engine E. The outer rotor 15 has aplurality of internal teeth 15A meshing with the external teeth 14A ofthe inner rotor 14, and is rotatably supported around a driven shaftcore Y (example of a second shaft core) which is eccentric from thedriving shaft core X.

The pump unit P is also referred to as an internal gear type. Theexternal teeth 14A of the inner rotor 14 are formed in a tooth surfaceshape following a mathematical curve. The teeth number of the internalteeth 15A of the outer rotor 15 is set to be one more than the teethnumber of the external teeth 14A of the inner rotor 14.

The adjustment mechanism 20 includes an adjustment ring 21 (example ofan adjustment member) which rotatably accommodates the outer rotor 15,an arm portion 22 formed integrally with the adjustment ring 21, and acompression coil-type adjustment spring 23 (example of a biasingmechanism) which applies a biasing force to the arm portion 22. In theadjustment mechanism 20, a guide pin 24 to be fixed to the housing H isinserted into a pair of elongated guide holes 21A formed in theadjustment ring 21. In this manner, the adjustment ring 21 is operatedin a state of being guided by the pair of guide pins 24.

In addition, oil seals 25 for maintaining a sealed state even when theadjustment ring 21 is operated are respectively provided at twolocations on an outer periphery of the adjustment ring 21 and in aprotruding end of the arm portion 22. In this manner, on an outerperipheral side of the adjustment ring 21 in an internal space of thehousing H, a low pressure chamber LS communicating with the suction port11, a high pressure chamber HS communicating with the discharge port 12,and the pressure chamber PS are formed. In particular, a control hole 16communicating with the control flow passage 5 is formed on a wallsurface of the housing H configuring the pressure chamber PS.

The adjustment ring 21 adjusts the discharge pressure of the oil in thedischarge port 12 by changing a positional relationship between thedriving shaft core X and the driven shaft core Y. Specifically, theadjustment mechanism 20 operates the adjustment ring 21 in a state ofbeing guided by the pair of guide pins 24. In this manner, the outerrotor 15 is moved in a form where the driven shaft core Y revolvesaround the driving shaft core X. According to this movement, a meshingrelationship in a pressurizing region between the external teeth 14A ofthe inner rotor 14 and the internal teeth 15A of the outer rotor 15 ischanged so as to realize adjustment of the discharge pressure of theoil. As a result of adjusting the discharge pressure, a discharge amountof the oil is also adjusted.

In addition, in a case where the adjustment ring 21 (arm portion 22)adopts a posture illustrated in FIG. 2, a meshing depth between theexternal teeth 14A of the inner rotor 14 and the internal teeth 15A ofthe outer rotor 15 in the discharge port 12 is greatly changed.Accordingly, the discharge pressure of the oil is maximized (pumpcapacity is maximized). In a case where the adjustment ring 21 (armportion 22) adopts a posture illustrated in FIG. 3, the meshing depthbetween the external teeth 14A of the inner rotor 14 and the internalteeth 15A of the outer rotor 15 in the discharge port 12 is lesschanged. Accordingly, the discharge pressure of the oil is minimized(pump capacity is minimized).

Furthermore, the biasing force of the adjustment spring 23 is appliedfrom the pump unit P in a direction in which the discharge pressure ofthe oil is increased. In this manner, the pressure of the pressurechamber PS is controlled so that the adjustment ring 21 is operatedagainst the biasing force of the adjustment spring 23. Accordingly, theoil can be supplied in a state where the discharge pressure is set toany desired value.

The pump unit P adopts a configuration in which the inner rotor 14 isrotationally driven and rotated using the drive shaft 13 driven by theengine E. However, a configuration may be adopted in which the outerrotor 15 is rotationally driven using a drive force of the engine E.

Pump Unit: Capacity Control

In a case where the drive current is not supplied to the solenoid valveV when the engine E is operated, the oil of the pressure chamber PS isdischarged outward via the drain flow passage 6. Accordingly, thepressure of the pressure chamber PS is equal to an atmospheric pressure.In this manner, the adjustment ring 21 is caused to maintain the postureillustrated in FIG. 2 by the biasing force of the adjustment spring 23,and the discharge pressure of the oil in the discharge port 12 ismaximized (flow rate is maximized).

Therefore, as when the engine E starts, in a situation where therotation speed of the engine E is low and the oil amount decreases, evenif the control unit C does not perform controlling to supply the drivecurrent to the solenoid valve V, the oil amount required for thehydraulic pressure actuator 3 or the main gallery 4 is supplied.

In addition, in a case where it is necessary to adjust the dischargepressure (discharge amount) from the pump unit P to the supply flowpassage 2, the control unit C adjusts the drive current to be suppliedto the solenoid valve V so as to control the oil pressure supplied fromthe solenoid valve V to the pressure chamber PS via the control flowpassage 5. In this manner, the adjustment ring 21 is operated integrallywith the arm portion 22 up to a position corresponding to the oilpressure applied to the pressure chamber PS. Accordingly, the adjustmentof the discharge pressure (discharge amount) of the oil is realized.

The pump unit P includes a bypass flow passage 26 which causes the fluidof the discharge port 12 to flow into the suction port 11, and a reliefvalve 27 disposed in the bypass flow passage 26. The relief valve 27 isconfigured to be brought into an open state if the discharge pressure ofthe discharge port 12 is equal to or more than a predetermined value. Ahydraulic pressure sensor SP is provided on the discharge port 12 sideof the pump unit P (refer to FIG. 1).

Control Unit

As illustrated in FIG. 4, the control unit C includes a region settingunit 31, a pressure value conversion unit 32, a map data selection unit33, and an output current control unit 34.

In the control unit C, the region setting unit 31, the pressure valueconversion unit 32, the map data selection unit 33, and the outputcurrent control unit 34 are configured to adopt software. However, thesemay be configured to adopt hardware, or may be configured to adopt acombination of the hardware and the software.

A measuring signal of the rotation speed sensor SR and a measuringsignal of the temperature sensor ST are input to the region setting unit31. Based on combinations of the rotation speed of the engine E (drivesource) and the oil temperature (temperature of the fluid) of the oil,in the region setting unit 31, an upper limit value Max (example of themaximum discharge pressure) and a lower limit value Min (example of theminimum discharge pressure) of the hydraulic pressure which can bedischarged in each combination are stored in advance. If the targethydraulic pressure is input to the pressure value conversion unit 32, asillustrated in FIG. 5, the region setting unit 31 specifies the upperlimit value Max and the lower limit value Min of the hydraulic pressurewhich can be discharged, based on the rotation speed of the engine Emeasured by the rotation speed sensor SR at that time and the oiltemperature measured by the temperature sensor ST at that time. Theregion setting unit 31 outputs the upper limit value Max and the lowerlimit value Min of the specified hydraulic pressure to the pressurevalue conversion unit 32. The pressure value conversion unit 32 sets theinput upper limit value Max and the input lower limit value Min in adefinition region D, and performs conversion so as to fall within arange of 0 to 1 (range in a vertical axis direction). In the definitionregion D, the upper limit value Max and the lower limit value Min whichare set based on the rotation speed of the engine E (drive source) andthe oil temperature of the oil are respectively defined as a maximumvalue and a minimum value in a predetermined range.

Specifically, in the definition region D of 0 to 1, the upper limitvalue Max expressed by MPa (mega Pascal) is converted into “1”, and thelower limit value Min expressed by MPa (mega Pascal) is converted into“0”.

Thereafter, in the pressure value conversion unit 32, in the definitionregion D, the input target hydraulic pressure is converted into aconversion target hydraulic pressure (example of a conversion targetdischarge pressure) having position information within the predeterminedrange. That is, in a state where the upper limit value Max is associatedwith a value of “1” in the definition region D and the lower limit valueMin is associated with a value of “0”, the target hydraulic pressurebetween the upper limit value Max and the lower limit value Min isconverted by the pressure value conversion unit 32, and is provided as anumerical value included in the range of 0 to 1. The numerical valueobtained by converting the target hydraulic pressure in this way iscalled the conversion target hydraulic pressure. The specifiedconversion target hydraulic pressure is output to the output currentcontrol unit 34.

As illustrated in FIG. 6, the map data M has a data structurerepresented by an orthogonal coordinate system in which the definitionregion D in the range of 0 to 1 is denoted in a direction of a verticalaxis (target axis) and the target current value is denoted in adirection of a horizontal axis (output axis) orthogonal to the verticalaxis (target axis).

As illustrated in FIG. 6, the map data M is configured to include anupper limit line portion Ma, a lower limit line portion Mb, and aconversion line portion Mc. In order to realize the target hydraulicpressure, the target current value for supplying power to the solenoidvalve V is acquired from the map data M as the target current value forthe conversion target hydraulic pressure obtained by converting thetarget hydraulic pressure.

As the specific map data M, the map data selection unit 33 mainly storesfirst map data M1 indicating a relationship between the conversiontarget hydraulic pressure and the target current value when the reliefvalve 27 is brought into an open state in the maximum dischargepressure, and a second map data M2 indicating a relationship between theconversion target hydraulic pressure and the target current value whenthe relief valve 27 is brought into a closed state in the maximumdischarge pressure. As illustrated in FIG. 7, the map data selectionunit 33 according to the present embodiment stores a total of threeitems of the map data such as one item of the first map data M1 and twoitems of second map data M2A and M2B. Out of the two items of the secondmap data M2A and M2B, the second map data M2A is applied to a case wherethe rotation speed of the engine E is greater than a predeterminedvalue, and the second map data M2B is applied to a case where therotation speed of the engine E is smaller than the predetermined value.

The first map data M1, the second map data M2A, and the second map dataM2B are prepared by aggregating a plurality of items of the map dataformed using a relationship between the discharge pressure and thecurrent value which are set in accordance with the rotation speed of theengine E in predetermined oil temperatures (0° C., 30° C., 60° C., and90° C.) illustrated in FIGS. 8 to 11.

FIGS. 8 to 11 are graphs illustrating each change in the dischargepressure which results from an increase in the current value whendifferent rotation speeds are set in a case where the oil temperaturesare respectively 0° C., 30° C., 60° C., and 90° C. In FIGS. 8 to 11, thevertical axis of the upper graph shows an actual value of the dischargepressure, and the vertical axis of the lower graph shows that the upperlimit value Max and the lower limit value Min of the discharge pressureof the upper graph are converted into the definition region D. The uppergraph shows a plurality of items of the map data. However, when the mapdata has the same current value, the rotation speed of the engine E islowered as the discharge pressure is lowered.

In FIG. 8 illustrating a case where the oil temperature of the oil is 0°C., if the upper graphs of the respective rotation speeds are convertedso that the vertical axis shows the definition region D, the lowergraphs show the result. The lower graphs substantially overlap eachother regardless of the rotation speed. The lower graphs can beaggregated in one type of graph, that is, the first map data M1illustrated in FIG. 7. On the other hand, in FIGS. 9 to 11 illustratinga case where the oil temperatures of the oil are respectively 30° C.,60° C., and 90° C., if the upper graphs of the respective rotationspeeds are converted so that the vertical axis shows the definitionregion D to become the lower graphs, the converted graphs can beaggregated into the first map data M1 when the rotation speed of theengine E is high. As the rotation speed decreases, the converted graphscan be aggregated into the second map data M2A, and further into thesecond map data M2B.

The first map data M1 illustrated in FIGS. 7 and 8 to 11 is a graphobtained by aggregating changes in the discharge pressure when therotation speed of the engine E is high and the relief valve 27 isbrought into the open state in the maximum discharge pressure. Thesecond map data M2A which is one of the items of the second map data M2is a graph obtained by aggregating changes in the discharge pressurewhen the rotation speed of the engine E is approximately medium and therelief valve 27 is brought into the closed state in a state where themaximum discharge pressure is equal to or more than a predeterminedvalue. The second map data M2B which is one of the items of the secondmap data M2 is a graph obtained by aggregating changes in the dischargepressure when the rotation speed of the engine E is low and the reliefvalve 27 is brought into the closed state in a state where the maximumdischarge pressure is equal to or smaller than predetermined value.

The first map data M1 shows a characteristic that the discharge pressureis not changed until the relief valve 27 is closed by applying thecurrent to the solenoid valve V, and that the discharge pressure startsto be greatly lowered when the discharge pressure exceeds apredetermined current value. On the other hand, the map data M2A and M2Bshow a characteristic that the discharge pressure is gradually loweredby applying the current to the solenoid valve V, and that the dischargepressure starts to be greatly lowered when the discharge pressureexceeds the predetermined current value. A value of the dischargepressure which brings the relief valve 27 into the open state in thepump device 100 can be calculated using a structure or a test operationof the pump device 100.

Based on a progress in the discharge pressure illustrated in FIGS. 8 to11, the map data M corresponding to the rotation speed of the engine Eand the oil temperature of the oil which are measured from the first mapdata M1, the second map data M2A, and the second map data M2B isselected. In this manner, for example, a map data correspondence tableillustrated in FIG. 12 can be obtained. The map data selection unit 33stores a plurality of items of the map data M1, M2A, and M2B, and themap data correspondence table. Based on the rotation speed of the engineE measured by the rotation speed sensor SR and the oil temperature ofthe oil measured by the temperature sensor ST, the map data selectionunit 33 refers to the map data correspondence table (for example, FIG.12), and selects whether to apply any one of the first map data M1, thesecond map data M2A, and the second map data M2B. The applied map data Mis output to the output current control unit 34, and the output currentcontrol unit 34 determines an instruction current value, based on theinput conversion target hydraulic pressure and the map data M selectedby the map data selection unit 33.

In this manner, in a situation where the target hydraulic pressure inputto the pressure value conversion unit 32 is constant, it is possible toacquire a proper target current value to be applied to the solenoidvalve V with reference to the map data M selected in the map dataselection unit 33. In a case where any one of the rotation speed of theengine E and the oil temperature fluctuates, the upper limit value Maxand the lower limit value Min which are set by the region setting unit31 are changed. In conjunction therewith, the conversion targethydraulic pressure in the definition region D is changed. Accordingly,the map data selection unit 33 newly selects the map data Mcorresponding to the changed rotation speed of the engine E and thechanged oil temperature from the map data correspondence table. Thepressure value conversion unit 32 converts the input target hydraulicpressure into the new conversion target hydraulic pressure, and theoutput current control unit 34 applies the new target current valuecorresponding to the new conversion target hydraulic pressure to thesolenoid valve V.

According to the present embodiment, the actual discharge pressure(actual hydraulic pressure) measured by the hydraulic pressure sensor SPis input to the output current control unit 34. In the output currentcontrol unit 34, the target current value is controlled to be fed back,based on the discharge pressure measured by the hydraulic pressuresensor SP. Specifically, the actual discharge pressure (actual hydraulicpressure) and the target hydraulic pressure corresponding to the targetcurrent value obtained with reference to the map data M are comparedwith each other. In a case where there is a difference between both ofthese, the target current value is corrected, based on the difference.In this manner, the discharge pressure of the pump unit P can coincidewith (or approximate to) the target hydraulic pressure. The outputcurrent control unit 34 may be configured so that the feedback controlbased on a measured value of the hydraulic pressure sensor SP is notperformed.

Control Form

A flowchart in FIG. 13 shows a schematic control configuration in adischarge pressure control routine performed by the control unit C. Ifthe control starts, based on the map data correspondence table, the mapdata selection unit 33 selects the map data M corresponding to therotation speed (the rotation speed per unit time) of the engine Emeasured by the rotation speed sensor SR and the oil temperature of theoil measured by the temperature sensor ST. In parallel therewith, basedon the rotation speed measured by the rotation speed sensor SR and theoil temperature measured by the temperature sensor ST, the regionsetting unit 31 specifies the upper limit value Max and the lower limitvalue Min which enable the target hydraulic pressure to be obtained, andoutputs the upper limit value Max and the lower limit value Min to thepressure value conversion unit 32. The pressure value conversion unit 32converts the upper limit value Max and the lower limit value Min so asto show the definition region D in which the upper limit value Maxcorresponds to “1” and the lower limit value Min corresponds to “0”(Step #101 and Step #102).

According to this control, based on the rotation speed of the engine Emeasured by the rotation speed sensor SR and the oil temperature of theoil, the map data M corresponding to the rotation speed and the oiltemperature is selected from a plurality of items of the map data M1,M2A, and M2B stored in the map data selection unit 33 with reference tothe map data correspondence table, and a process for outputting(loading) the map data M to the output current control unit 34 isperformed. In addition, based on the rotation speed measured by therotation speed sensor SR and the oil temperature measured by thetemperature sensor ST, the region setting unit 31 specifies the upperlimit value Max and the lower limit value Min, and the pressure valueconversion unit 32 sets the definition region D.

If the target hydraulic pressure is input to the pressure valueconversion unit 32, the target hydraulic pressure is converted into theconversion target hydraulic pressure within a range of the definitionregion D. According to this control, the target hydraulic pressureserving as a real value is converted into the conversion targethydraulic pressure which is a numerical value included within the rangeof 0 to 1 corresponding to the definition region D (Step #103 and Step#104).

The conversion target hydraulic pressure converted from the targethydraulic pressure in the pressure value conversion unit 32 is output tothe output current control unit 34. From the loaded map data M and theinput conversion target hydraulic pressure, the output current controlunit 34 acquires the target current value corresponding thereto, andoutputs the current value corresponding to the target current value tothe solenoid valve V (Step #105 and Step #106).

As described above, the first map data M1 and the second map data M2(M2A and M2B) which are set depending on whether or not the maximumdischarge pressure is the discharge pressure for bringing the reliefvalve 27 into an open state have inherent characteristics. Therefore,any one of the first map data M1 and the second map data M2 (M2A andM2B) is selected, based on the rotation speed of the engine E measuredby the rotation speed sensor SR and the oil temperature of the oil. Inthis manner, in order to obtain the target discharge pressurecorresponding to the rotation speed of the engine E and the oiltemperature of the oil from the selected map data M, it is possible toproperly set the target current value to be supplied to the solenoidvalve V. In this manner, it is possible to reduce the number of items ofthe map data to be referenced. Therefore, the storage capacity of themap can be minimized in the control unit C, and the calculation processof the target current value can be simplified.

In a case where the maximum discharge pressure has a magnitude so thatthe relief valve 27 is not brought into the open state, the map dataselection unit 33 selects the second map data M2. Here, as illustratedin FIGS. 9 to 11, in the maximum discharge pressure which has amagnitude so that the relief valve 27 is not brought into the openstate, a pressure (for example, a medium pressure) slightly lower thanthe discharge pressure which brings the relief valve 27 into the openstate and a considerably low pressure (for example, a low pressure) aremixed with each other. For example, if the maximum discharge pressure isthe low pressure, the pressure applied to the adjustment member is low.Accordingly, in some cases, the pump device may be greatly affected bythe biasing mechanism which biases the adjustment member in thedirection in which of the discharge pressure is increased or decreased.On the other hand, in a case where the maximum discharge pressure is themedium pressure, the pump device is less affected by the biasingmechanism, and the pressure applied to the adjustment member becomesdominant. Therefore, in the maximum discharge pressure which has amagnitude so that the relief valve 27 is not brought into the openstate, in some cases, a progress of the map data may greatly varydepending on a magnitude of the discharge pressure.

Therefore, according to this configuration, two items of the second mapdata M2A and M2B are stored in the map data selection unit 33. In thismanner, in accordance with to the rotation speed of the engine E and theoil temperature of the oil, the map data selection unit 33 can selectthe proper map data M in which the maximum discharge pressure is set tohave a magnitude so that the relief valve 27 is not brought into theopen state. As a result, in order to obtain the target dischargepressure corresponding to the rotation speed and the oil temperature, itis possible to accurately set the target current value to be supplied tothe solenoid valve V.

Other Embodiments

In the above-described embodiment, an example has been described inwhich the map data selection unit 33 stores two items of the map dataM2A and M2B as the second map data M2. However, the number of items ofthe second map data M2 is not limited to two. In a case where the mapdata is less changed even if the upper limit value Max (maximumdischarge pressure) which has a magnitude so that the relief valve 27 isnot brought into the open state is raised or lowered, the number ofitems of the second map data M2 may be one. In addition, in order tofurther improve the accuracy of the target current value to be suppliedto the solenoid valve V, the number of items of the second map data M2may be three or more.

In the above-described embodiment, an example has been described inwhich the definition region D falls within the range of 0 to 1. However,alternatively, the definition region D may fall within a range set usingany desired numerical value.

Embodiments disclosed here can be widely utilized for a pump devicehaving a variable capacity-type pump unit and a control unit.

A feature of a pump device according to an aspect of this disclosureresides in that the pump device includes a variable capacity-type pumpunit configured to include an inner rotor having a plurality of externalteeth and rotatable around a first shaft core, an outer rotor having aplurality of internal teeth meshing with a portion of the plurality ofexternal teeth of the inner rotor and rotatable around a second shaftcore, a housing accommodating the inner rotor and the outer rotor, asuction port and a discharge port which are formed in the housing, anadjustment member rotatably supporting the outer rotor and adjusting adischarge pressure of a fluid in the discharge port by changing apositional relationship between the first shaft core and the secondshaft core, a biasing mechanism biasing the adjustment member in adirection in which the discharge pressure is increased or decreased, acontrol flow passage causing a fluid pressure from the discharge port tobe applied to the adjustment member to apply a pressure to theadjustment member against a biasing force of the biasing mechanism, asolenoid valve interposed in the control flow passage in order to adjustthe fluid pressure to be applied to the adjustment member, a bypass flowpassage causing the fluid of the discharge port to flow into the suctionport, and a relief valve disposed in the bypass flow passage so as to bebrought into an open state when the discharge pressure reaches apredetermined value or more, a rotation speed sensor measuring arotation speed per unit time of a drive source that drives the innerrotor or the outer rotor, and a control unit controlling the solenoidvalve. The control unit includes a pressure value conversion unit thatconverts a target discharge pressure into a conversion target dischargepressure serving as position information within a predetermined range,in a definition region where a maximum discharge pressure and a minimumdischarge pressure which are set based on the rotation speed of thedrive source and a temperature of the fluid are respectively defined asa maximum value and a minimum value in the predetermined range, a mapdata selection unit that stores first map data in which the relief valveis brought into an open state in the maximum discharge pressure andsecond map data in which the relief valve is brought into a closed statein the maximum discharge pressure, as map data having a data structurerepresented by an orthogonal coordinate system in which the definitionregion is denoted in a direction of a target axis and a target currentvalue of the solenoid valve is denoted in a direction of an output axisorthogonal to the target axis, and that selects any one of the first mapdata and the second map data, based on the rotation speed of the drivesource measured by the rotation speed sensor and the temperature of thefluid measured by a temperature sensor, and an output current controlunit that acquires the target current value corresponding to theconversion target discharge pressure with reference to the selected mapdata, and that outputs the target current value to the solenoid valve.

According to this configuration, in a case where the target dischargepressure is acquired, the control unit causes the pressure valueconversion unit to convert the target discharge pressure into theconversion target discharge pressure. Next, the map data selection unitselects by one of the first map data when the relief valve is in an openstate and the second map data when the relief valve is in a closedstate, which are stored as the map data, based on the rotation speed ofthe drive source measured by the rotation speed sensor and thetemperature of the fluid measured by the temperature sensor. Next, theoutput current control unit acquires the target current valuecorresponding to the conversion target discharge pressure with referenceto the selected map data, and outputs the target current value to thesolenoid valve.

Even though the target discharge pressure has the same value, thecurrent value to be supplied to the solenoid valve varies correspondingto the rotation speed of the drive source and the temperature of thefluid. For this reason, it is necessary to prepare the map datacorresponding to the rotation speed of the drive source and thetemperature of the fluid.

In this case, if it is considered that the target current value isacquired with reference to the map data by using the target dischargepressure expressed in units of MPa (mega Pascal), it is necessary toprepare the data structure on which the target discharge pressure andthe target current value corresponding to units of MPa are reflected asthe map data. However, in the data structure configured in this way, ina case where the rotation speed of the drive source or the temperatureof the fluid is changed, the map data needs to be corrected or modifiedin order to cope with this change, or the map data needs to be newlyset. In a case where the map data is newly prepared, it is necessary toprovide multiple items of the map data in advance.

In contrast, according to this configuration, the definition region isdefined in which the maximum discharge pressure and the minimumdischarge pressure which are set based on the rotation speed of thedrive source and the temperature of the fluid are respectively set asthe maximum value and the minimum value in the predetermined range. Thepressure value conversion unit converts the target discharge pressureinto the conversion target discharge pressure serving as the positioninformation within the predetermined range. Then, the map data has thedata structure represented by the orthogonal coordinate system in whichthe definition region is denoted in the direction of the target axis andthe target current value of the solenoid valve is denoted in thedirection of the output axis orthogonal to the target axis. The map datais configured to include the first map data when the relief valve isbrought into an open state in the maximum discharge pressure and thesecond map data when the relief valve is brought into a closed state inthe maximum discharge pressure.

In a case where the maximum discharge pressure set based on the rotationspeed of the drive source measured by the rotation speed sensor and thetemperature of the fluid measured by the temperature sensor is highenough to bring the relief valve into the open state, the first map datais selected. The first map data has a characteristic that the dischargepressure is not changed until the relief valve is closed by applying thecurrent to the solenoid valve and the discharge pressure starts to begreatly lowered when the discharge pressure exceeds a predeterminedcurrent value. On the other hand, in a case where the maximum dischargepressure has a magnitude so that the relief valve is not brought intothe open state, the second map data is selected. The second map data hasa characteristic that the discharge pressure is gradually lowered byapplying the current to the solenoid valve and the discharge pressurestarts to be greatly lowered when the discharge pressure exceeds thepredetermined current value. A value of the discharge pressure whichbrings the relief valve into the open state in the pump device can becalculated using a structure or a test operation of the pump device.

In this way, the first map data and the second map data which are setaccording to whether or not the maximum discharge pressure is thedischarge pressure for bringing the relief valve into the open statehave inherent characteristics. Therefore, any one of the first map dataand the second map data is selected, based on the maximum dischargepressure. In this manner, it is possible to properly set the targetcurrent value to be supplied to the solenoid valve in order to obtainthe target discharge pressure corresponding to the rotation speed of thedrive source and the temperature of the fluid from the selected mapdata. In this manner, it is possible to reduce the number of items ofthe map data to be referenced. Accordingly, storage capacity of the mapcan be minimized in the control unit, and a calculation process of thetarget current value can be simplified.

Therefore, one is selected from two items of the map data in accordancewith the maximum discharge pressure. In this manner, it is possible toproperly set the target current value to be supplied to the solenoidvalve in order to obtain the target discharge pressure corresponding tothe rotation speed and the temperature of the fluid. As a result, thestorage capacity of the map can be minimized in the control unit, andthe calculation process of the target current value can be simplified.

Another feature resides in that the map data selection unit stores aplurality of items of the second map data in accordance with an upperlimit value of the target discharge pressure based on the rotation speedof the drive source and the temperature of the fluid.

In a case where the maximum discharge pressure has a magnitude so thatthe relief valve is not brought into the open state, the second map isselected as the map data. However, in the maximum discharge pressurewhich is not high enough to bring the relief valve into the open state,a pressure (medium pressure) slightly lower than the discharge pressurewhich brings the relief valve into the open state and a considerably lowpressure (low pressure) are mixed with each other. For example, in acase where the maximum discharge pressure is the low pressure, thepressure applied to the adjustment member is low. Accordingly, in somecases, the pump device may be greatly affected by the biasing mechanismwhich biases the adjustment member in the direction in which thedischarge pressure is increased or decreased. On the other hand, in acase where the maximum discharge pressure is the medium pressure, thepump device is less affected by the biasing mechanism, and the pressureapplied to the adjustment member becomes dominant. Therefore, in themaximum discharge pressure which has a magnitude so that the reliefvalve is not brought into the open state, it is considered that the mapdata may greatly vary depending on the discharge pressure.

Therefore, according to this configuration, the map data selection unitstores a plurality of items of the second map data in accordance withthe upper limit value of the target discharge pressure, based on therotation speed of the drive source and the temperature of the fluid. Inthis manner, the proper map data in which the maximum discharge pressureis set to have a magnitude so that the relief valve is not brought intothe open state can be selected in accordance with the rotation speed andthe temperature of the fluid. As a result, it is possible to accuratelyset the target current value to be supplied to the solenoid valve inorder to obtain the target discharge pressure corresponding to therotation speed and the temperature of the fluid.

Another feature resides in that the pump device further includes ahydraulic pressure sensor measuring the discharge pressure, and thetarget current value is controlled to be fed back, based on thedischarge pressure measured by the hydraulic pressure sensor.

Similarly to this configuration, if the target current value iscontrolled to be fed back based on the discharge pressure measured bythe hydraulic pressure sensor, in a case where an actual dischargepressure and the target hydraulic pressure do not coincide with eachother, the target current value can be easily adjusted. In this manner,the discharge pressure of the electric pump can coincide with (orapproximate to) the target hydraulic pressure.

The principles, preferred embodiment and mode of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiments disclosed. Further,the embodiments described herein are to be regarded as illustrativerather than restrictive. Variations and changes may be made by others,and equivalents employed, without departing from the spirit of thepresent invention. Accordingly, it is expressly intended that all suchvariations, changes and equivalents which fall within the spirit andscope of the present invention as defined in the claims, be embracedthereby.

What is claimed is:
 1. A pump device comprising: a variablecapacity-type pump unit configured to include an inner rotor having aplurality of external teeth and rotatable around a first shaft core, anouter rotor having a plurality of internal teeth meshing with a portionof the plurality of external teeth of the inner rotor and rotatablearound a second shaft core, a housing accommodating the inner rotor andthe outer rotor, a suction port and a discharge port which are formed inthe housing, an adjustment member rotatably supporting the outer rotorand adjusting a discharge pressure of a fluid in the discharge port bychanging a positional relationship between the first shaft core and thesecond shaft core, a biasing mechanism biasing the adjustment member ina direction in which the discharge pressure is increased or decreased, acontrol flow passage causing a fluid pressure from the discharge port tobe applied to the adjustment member to apply a pressure to theadjustment member against a biasing force of the biasing mechanism, asolenoid valve interposed in the control flow passage in order to adjustthe fluid pressure to be applied to the adjustment member, a bypass flowpassage causing the fluid of the discharge port to flow into the suctionport, and a relief valve disposed in the bypass flow passage so as to bebrought into an open state when the discharge pressure reaches apredetermined value or more; a rotation speed sensor measuring arotation speed per unit time of a drive source that drives the innerrotor or the outer rotor; and a control unit controlling the solenoidvalve, wherein the control unit includes a pressure value conversionunit that converts a target discharge pressure into a conversion targetdischarge pressure serving as position information within apredetermined range in a definition region where a maximum dischargepressure and a minimum discharge pressure which are set based on therotation speed of the drive source and a temperature of the fluid arerespectively defined as a maximum value and a minimum value in thepredetermined range, a map data selection unit that stores first mapdata in which the relief valve is brought into an open state in themaximum discharge pressure and second map data in which the relief valveis brought into a closed state in the maximum discharge pressure, as mapdata having a data structure represented by an orthogonal coordinatesystem in which the definition region is denoted in a direction of atarget axis and a target current value of the solenoid valve is denotedin a direction of an output axis orthogonal to the target axis, and thatselects any one of the first map data and the second map data based onthe rotation speed of the drive source measured by the rotation speedsensor and the temperature of the fluid measured by a temperaturesensor, and an output current control unit that acquires the targetcurrent value corresponding to the conversion target discharge pressurewith reference to the selected map data, and that outputs the targetcurrent value to the solenoid valve.
 2. The pump device according toclaim 1, wherein the map data selection unit stores a plurality of itemsof the second map data in accordance with the maximum dischargepressure.
 3. The pump device according to claim 1, further comprising: ahydraulic pressure sensor measuring the discharge pressure, wherein thetarget current value is controlled to be fed back, based on thedischarge pressure measured by the hydraulic pressure sensor.